Unlike with in the "toll-house of envy" in which I mentioned I couldn't see what made it represent Envy, this one is quite clear for me. It is not as obvious as Gluttony were we had that large worm-like creature or Laziness in which the pose played and important part in the picture, the creature seems reluctant to do anything, but there is also the "comfortable bed". In this case, the pose is everything, it is as if the Demon of Pride is looking at the newcomer souls in a haughty manner, in other words, full of its own Pride. Just perfect